This invention relates to a sewing machine needle.
Generally, sewing machines have a needle which, in the vicinity of its point, has an eye through which an upper thread is guided. During sewing, the needle pierces through the material to be sewn (flat textile fabric) and, as a result of a stepwise feed of the fabric, the needle produces spaced stitch holes. The upper thread is guided from stitch hole to stitch hole, and during this occurrence the thread glides over an edge of the eye both in the forward and in the reverse direction. When the feed direction of the fabric is determined, the needle has a fixed working direction and the fabric is advanced in a fixed direction which, as a rule, is oriented transversely to the eye.
It has been found, however, that in sewing machines which provide for a fabric feed in different directions, for example, in forward and rearward directions or in several other directions, the seam quality depends from the sewing direction and/or the thread twist. Such a dependence is often not desirable.
German Utility Model 86 32 106.4 discloses a tufting needle which has, in the direction of the needle axis, an elongated eye provided at both ends with respective curved upper and lower eye edges. At the outlet side the eye edge is straight. The tufting needle is of asymmetrical construction as seen in top plan view, that is, in the direction of the eye axis. On the outlet side the eye adjoins a curved thread trough. A tufting needle of this type has a preferred working direction.
In contrast, U.S. Pat. No. 3,986,468 discloses a symmetrical needle for a sewing machine. In the vicinity of its point, the needle has an eye extending transversely through the needle body and bounded by two eye walls. Both eye walls have straight edges at their upper as well as at their lower sides, that is, the edges of the side walls extend in each instance along a straight line from the eye end oriented toward the needle shank (clamping portion) to the eye end oriented toward the needle point. Although such needles are of symmetrical construction, they have a different behavior for a forward sewing and a reverse sewing with twisted threads.